Stormwater Wetland Design Criteria

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Design Criteria
Shallow Wetland
Pond/Wetland
ED Shallow Wetland*
Wetland/Watershed Ratio (Ac/Ac)
0.2
0.1
0.1
Minimum Drainage Area (Ac)
25
10
25
Length to Width Ratio (minimum)(ft/ft)
2:1
2:1
2:1
Extended Detention (ED)
No
Optional
Yes
Allocation of Vwq (pool/marsh/ED) in %
25/75/0
70/30/0(includes pond volume)
25/25/50
Allocation of Surface Area (deepwater/low marsh/high marsh/semi-wet) in %
20/35/40/5
45/25/25/5 (includes pond surface area)
10/35/45/10
Forebay
Required
Required
Required
Micropool
Required
Required
Required
Outlet Configuration
Reverse-slope pipe or hooded broad-crested weir
Reverse-slope pipe or hooded broad-crested weir
Reverse-slope pipe or hooded broad-crested weir

*Note: The ED Shallow Wetland design guidance does not meet the MPCA requirements for permanent volume. The guidance may be applied in a stormwater retrofit situation where area requirements preclude the use of a Shallow Wetland

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